January 2011: D.C.'s second straight cold month
Our cold winter marches onward. For the second month in a row, Washington D.C. was colder-than-average. But, January 2011 wasn't as strong of a cold anomaly as December as the average temperature at Reagan National Airport was only 1.3F colder than the 30-year (1971-2000) normal.
Like December, I looked at January 2011 in the context of the historical record to see if we can see anything significant. It turns out that January 2011 was the 21st coldest January in the sixty-one year historical record back to 1950. (If you go back to 1871, it was tied for the 56th coldest year with 1910. However, D.C.'s observing site was in different locations prior to the early 1940s when it moved to National Airport.) The average temperature of 33.6F was colder than any decadal average January temperature back to the 1950.
I was surprised to see how warm the 1950s were around here, but warmth was focused the front part of that decade. January 1950 featured the warmest high temperature of the month in DC history- a balmy 79F on January 26! Overall, the 1990s were the warmest decade- it only featured two colder-than-normal winters. You can see the trace of all Washington, D.C. January anomalies on the graph above.
There doesn't seem to be any discernible long-term trend for D.C. and January.
Washington, D.C. also picked up 7.3" of snow in January 2011, which is 1.1" above normal, but that is nowhere near the long-term record 31.5" from the downtown location in 1922. Melted (liquid) precipitation was just 2.25", almost one inch below average.
Jason Samenow pointed out to me that the National Weather Service creates really nifty monthly assessments usually within a week of the close of each month. You can click on your closest airport location here:
I highly recommend scrolling all the way to the bottom for all the fun trivia.
For example, January 2011 at DCA saw 19 of 31 days fail to reach 40F. The coldest low temperature at the airport this month was 17F, which was the coldest reading since February 2010's 16F reading. And this raises an interesting point- the average high temperature was 2.8F below normal, while the average low temperature was 0.3F above normal. The inability to get the low temperatures lower may stem from frequent cloud cover and winds (oh those winds) that kept the surface layer mixed.
From a big picture standpoint, the U.S. saw frequent cold opportunities due to a changing cast of pattern influences in January. The Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Eastern Pacific Oscillation (EPO) all conspired in their negative phases to deliver cold conditions to much of the U.S.
We are finally going to get a break from these powerhouse players next week in a sort of February thaw pattern (highs in the 50s and maybe 60s!?!?), but there are signs that at least the negative NAO could come back to influence our weather late this month into early March.
Historical Washington, DC data provided by NOAA and Speedwell Weather.
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